Abstract:
Water is increasingly becoming a scarce resource as freshwater sources are
being depleted globally, leading to an increased interest in desalination, i.e. provision
of drinking water from the saline sea water. Most desalination technologies are energy
intensive while Microbial Desalination Cells (MDCs) represent a sustainable option
that has the added benefit of solving the ever increasing waste water management
problem. MDCs are a modified form of Microbial Fuel Cells (MFCs) that rely on the
potential created by organic media to reduce salt concentration by a phenomena called
electro-dialysis and provide renewable means of clean water production. The series of
experiments were carried out to check the desalination ability of an indigenously
designed experimental setup (Bio-electrochemical Assembly) using real domestic
waste water inoculated with sewage sludge of Membrane Bioreactor (MBR) under
standardized conditions. The electrochemical properties of the system, including
polarization curves and Electrochemical Impedance Spectroscopy (EIS) were studied
along with the extent of COD removal in order to characterize the cell. Acidic water
and Phosphate Buffer Solution (PBS) were tested as potential catholytes against which
the performance of the waste water was gauged at various salt concentrations. The
maximum salt removal efficiency was 31%, achieved at salt concentration of 35 g/L
that decreases with a reduction in salt concentration. The maximum current density
and power density was 246 mA/m2 and 32 mW/m2 respectively achieved using acidic
water catholyte. EIS experiments revealed that at higher salt concentrations internal
resistance of the cell is lowest. Results also depicted that in terms of efficiency and
economics acidic water type catholyte is more beneficial than the PBS.
